Modified FFC Cambridge Cell: Capabilities
I believe a modified FFC Cambridge Process cell operating at the standard 900°C, but including liquid/gas traps at the top of interchangeable
cathodes and a liquid trap at the bottom, as well as a gas trap over the anode, could be quite versatile. While such a cell would lack the efficiency
of other types of fused salt cells, it should be able to produce a very wide range of metals and non-metals. It may also be viable to lower the
melting point of the electrolyte to under 650°C by using a eutectic BaCl2-CaCl2 system.
If I understand the calcothermic reduction, such a cell should be able to produce liquid lithium, magnesium and aluminum, beryllium, all transition
metals and rare earth metals, boron, silicon, germanium, and gaseous sodium (possibly also gaseous potassium and lower alkali metals, since they would
be distilled out of equillibrium), from their oxides, sulfides, sulfates, or phosphates. There may be some exceptions in those groups but I cannot
think of any or why they would be. From scrap soda-lime glass it should be able to produce both gaseous sodium and powdered silicon in situ. Calcium
from the lime should enter the electrolyte as dissolved metal, where the excess could be precipitated out as lime by bubbling air into the cell near
the cathode and removing it with some sort of trap or filter. Alternatively chlorine could be added to the cell to scavenge the excess calcium, with
the excess calcium chloride then being tapped off.
If they are sparingly soluble in the electrolyte, calcium sulfate, sulfide, and phosphates should also be broken down in this manner, with the excess
calcium being precipitated as lime or tapped off as calcium chloride, and the anodic gas consisting of, respectively, SO3 + O2, sulfur, or P2O5 + O2.
According to the phase diagram of the CaCl2-CaO system, this precipitation should begin to occur with about 20% molar CaO in the electrolyte at
900°C, and would likely depend on the precipitate being promptly removed from the system.
During a run of any given material, several cathodes could be employed so that they may be easily exchanged upon depletion and replaced with freshly
loaded ones. The anode would likely consist of a finned steel or copper electrode coated with tin oxide, as this has been reported as the most
suitable coating material in a document on the development of the FFC Cambridge Process.
These renderings show what such a cell might look like. To change a cathode during a solid metal sponge process or sinking liquid metal process,
power to the given cathode would be disconnected and the empty cathode would simply be pulled out and replaced with a loaded one. For a floating
liquid metal process, the metal would be siphoned out of the trap and replaced with argon, by setting the siphon tube to the same level as the
electrolyte as determined by a level-sensing electrode. Some excess electrolyte may be sucked up the siphon tube, or some metal may be left in the
trap which would burn out once the cathode is lifted. For a gaseous metal process, the vapor would simply be purged through the condenser side-arm
(which was the argon source in a floating liquid metal process) with argon from the dip tube (which was the siphon tube in a floating liquid metal
process).
[Edited on 3-11-2008 by kilowatt]
The mind cannot decide the truth; it can only find the truth.
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